Kim, SH Kim, YH Cho, HN Kwon, SK Kim, HK Choi, SK 2024-01-21T19:31:56Z 2024-01-21T19:31:56Z 2022-01-10 1996-07-29 0024-9297 https://pubs.kist.re.kr/handle/201004/144380 We report here the effect of size and type of substituents upon the fine and conformational structure and unusual optical absorption behavior for the substituted poly(1,6-heptadiynes). 4-(Carboxy-3-(trimethylsilyl)-1-propyl)-1,6-heptadiyne (1a), 4,4-bis(3-(trimethylsilyl)-1-propyl) dipropargylmalonate (1b), 4,4-bis[(acetoxy)methyl]-1,6-heptadiyne (2a), 4,4-bis[(ethylcarboxy)methyl]-1,6-heptadiyne (2b), 4,4-bis[(tert-butyldimethylsiloxy)methyl]-1,6-heptadiyne (3a), and 4,4-bis[(tert-butyldiphenylsiloxy)methyl]-1,6-heptadiyne (3b) were all prepared and polymerized to give organo-soluble polymers in high yield with MoCl5-based catalysts. From a series of lambda(max) values of the polymers, we have found that incorporation of a bulkier substituent in the 4-position of 1,6-heptadiyne forces the conjugated polyene into a more planar structure, as indicated by the bathochromic shift of maximum absorption bands resulting from the pi-pi* transition of the conjugated polymer backbone. It appears that chain twisting of the substituted poly(1,6-heptadiynes) is determined primarily by the bulk of the substituent group at the 4-position rather than by the point of attachment to the polymer chain which usually decreases the effective conjugation length of the polymer pi-system. When an extremely bulky substituent was introduced at the 4-position, the resulting polymer had predominantly a symmetric single repeat unit with a five-membered ring and a trans vinylene group. The polymer 3b (lambda(max) = 606 nm) with a nearly 100% five-membered ring structure is environmentally very stable: there is no observable change in IR, NMR, and UV-visible spectra upon exposure to air for 6 weeks. This stability of backbone to air oxidation is thought to be due to effective shielding of the highly conjugated backbone by the bulky substituents. English AMER CHEMICAL SOC TRANSITION-METAL CATALYSTS CONJUGATED IONIC POLYACETYLENE LIQUID-CRYSTALLINE POLYMERS DIETHYL DIPROPARGYLMALONATE LIVING CYCLOPOLYMERIZATION METATHESIS POLYMERIZATION DERIVATIVES CHAIN Unusual optical absorption behavior, polymer structure, and air stability of poly(1,6-heptadiyne)s with substituents at the 4-position Article 10.1021/ma9507103 1 MACROMOLECULES, v.29, no.16, pp.5422 - 5426 MACROMOLECULES 29 16 5422 5426 scie scopus A1996VA22100025 2-s2.0-0030194042 Polymer Science Polymer Science Article TRANSITION-METAL CATALYSTS CONJUGATED IONIC POLYACETYLENE LIQUID-CRYSTALLINE POLYMERS DIETHYL DIPROPARGYLMALONATE LIVING CYCLOPOLYMERIZATION METATHESIS POLYMERIZATION DERIVATIVES CHAIN